minor #20255 [Doctrine] Delete the article about reverse engineering (javiereguiluz)

This PR was squashed before being merged into the 7.1 branch.

Discussion
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[Doctrine] Delete the article about reverse engineering

We soft-deleted this short article a few years ago, so we can fully delete it in 7.x branch.

Commits
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eacc9c3 [Doctrine] Delete the article about reverse engineering

Author: javiereguiluz

_build/redirection_map

@@ -571,3 +571,4 @@
 /testing/http_authentication /testing#testing_logging_in_users
 /doctrine/registration_form /security#security-make-registration-form
 /form/form_dependencies /form/create_custom_field_type
+/doctrine/reverse_engineering /doctrine#doctrine-adding-mapping

doctrine.rst

@@ -84,15 +84,15 @@ affect how Doctrine functions.
     There are many other Doctrine commands. Run ``php bin/console list doctrine``
     to see a full list.
 
+.. _doctrine-adding-mapping:
+
 Creating an Entity Class
 ------------------------
 
 Suppose you're building an application where products need to be displayed.
 Without even thinking about Doctrine or databases, you already know that
 you need a ``Product`` object to represent those products.
 
-.. _doctrine-adding-mapping:
-
 You can use the ``make:entity`` command to create this class and any fields you
 need. The command will ask you some questions - answer them like done below:
 
@@ -1107,7 +1107,6 @@ Learn more
     doctrine/dbal
     doctrine/multiple_entity_managers
     doctrine/resolve_target_entity
-    doctrine/reverse_engineering
     testing/database
 
 .. _`Doctrine`: https://www.doctrine-project.org/